#include <iostream>
#include <algorithm>
using namespace std;
#define int long long
const int N = 24;
int n, m, a, b;
int dp[N][N];
bool check(int i, int j)
{
    return (i == a && j == b) || (i != a && j != b && abs(i - a) + abs(j - b) == 3);
}
signed main()
{
    cin >> n >> m >> a >> b;
    n++, m++, a++, b++;

    dp[0][1] = 1;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            if (check(i, j))
                continue;
            dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
        }
    }
    cout << dp[n][m] << endl;
    return 0;
}